Definition 3 [1]}
For a hypothesis space \(H\) , the symmetric difference hypothesis space \(\mathcal {H}\Delta \mathcal {H}\)  is the set of hypotheses
\(g\in \mathcal {H}\Delta \mathcal {H} \Leftrightarrow g(\mathbf {x})=h(\mathbf {x})\oplus h^{\prime }(\mathbf {x})\)  forsome \(h,h^{\prime }\in \mathcal {H}\) ,
where \(\oplus \)  is the XOR function. That is, every hypothesis \(g\in \mathcal {H}\Delta \mathcal {H}\)  is the set of disagreements between two hypotheses in \(\mathcal {H}\) .

